So I got a message about a forgotten beast: an enormous condor with mandibles and a noxious secretion. Luckily there was no way the condor could enter my fort as I had sealed all accesses to the cavern.
Fast forward six months.
No condor to be seen, I want to expand my magma forges, so I pierce the cavern wall to channel some more magma to my forge areas. Of course, I forgot to build a new wall to replace the old one. And of course, the condor decided to make a visit. Mind you, I have 57 dwarves but a really weak militia, mainly copper weapons, very little armour (I was just starting my metal industry, found my first metal ores at z-40, while the magma pool was much higher), way too little military training for my dwarves.
And I managed to slay the beast with just one casualty.
That was because my expedition leader / miner was visiting the magma forges at just that time. One hit with a pick and the condor was unable to fly due to a damaged right wing. Then a bunch of ordinary freshly drafted dwarves (I drafted everyone because I was ready to go out in style) jumped on the immobile bird and began to punch and strangle and wrestle it. The condor managed to tear someone's artery to make him bleed to death in a few seconds, but apart from that it landed maybe three or four hits total. In the end the heroic expedition leader had enough mercy to deliver the last fatal blow to the surprisingly weak megabird.
I'm quite happy, the first forgotten beast I've managed to kill.
Edit: and now a mere hunter headshotted a kobold thief from miles away with a bone bolt, is this Sparta or something